99 4.0 idle but no speed up - Ranger-Forums - The Ultimate Ford Ranger Resource


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Old 12-07-2010
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99 4.0 idle but no speed up

hi all i hope someone can help me here im at my witts end on this! i have a 99 4.0 that will start and idle great no misses or anything but as soon as you start trying to speed it up it will go to about 1100 rpm then start bucking and popping and actimng like its running out of feul? they were driving down the road fine when it just died they said and now it will start and idle great, but no faster? i changed feul filter first thing and its a good thing i did i dont think it had ever been done and was filthy. but no change, there are no stored or pending codes and thats what gets me? i have kinda checked thru everything a little but i dont have a manual for this one as its not mine. so i dont know how to check the tps and stuff? i kinda am leaning towards the tps? sound like im heading the right way? if anyone has had this or a like problem i would love to hear from you. i saw one guy did but he didnt get any replies and threw a baby fit so i dont think hes here any more. i wont i swear. thanks again and any help appreciated im at a stop
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Old 12-07-2010
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Monitor voltage between the gray/white and gray/red wires of the TPS with everything plugged in normally. Closed throttle voltage should be between 0.53v and 1.27v although most are usually nearer to 1.00v from the factory. As the throttle is opened, the voltage should increase proportonately along with it with no flat spots, dropouts or reversals. Max volts at WOT should be greater than 4 but less than 5 volts.

Could also be a weak pump, dirty/defective MAF sensor or ignition problems.
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Old 12-07-2010
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awesome thank you very much i will do that here in a few and get back with you to let you know wat i find thanks again
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Old 12-07-2010
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ok i checked those and the tps shows good by the tests and i cleaned and checked the maf and it was very clean? im leaning towards feull pump but i cannot find the shreader valve on the feul rail to hook into? it says it has one on the forums? do you have to break the line apart somewhere and have the adapter that goes inline maybe? thanks for your help
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Old 12-08-2010
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Your 4.0 SOHC Schrader valve is on the passenger side fuel rail all the way at the back toward the firewall. It came from the factory with a plastic cap on it, probably blue or black.
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Old 12-08-2010
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thanks a bunch ill find it then post results thanks again
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Old 12-08-2010
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what should the pressure be do u know?
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Old 12-08-2010
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64+/-8 PSI
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Old 12-08-2010
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ok when i checked the feul trim1, it was at 8.6% idleing and the feul trim 2 was 10.2% and you said if its more than 5 theres a problem? what and where would it be? the feul pressure is great turn key on and get 60 right away then satrt it and it goes to 65, then even when it start the bogging down and running crappy it still shows the feul pressure as no change and good? dang i aint getting no where fast. the customer is starting to wonder also and i dont want to just throw parts at it. thanks
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Old 12-08-2010
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I would try a few things;
  • Unplug the Mass Air Flow sensor and see if it likes that. When the MAF is offline, the PCM uses the TPS exclusively. If unplugging it helps, the MAF may have a problem.
  • Disconnect and plug the vacuum line to the EGR. If that helps, then there may a problem with flow sensing by the DPFE sensor.
  • Add propane when it is struggling. If that clears it up, at least we know that it's a lean condition.
  • Check spark during the problem.
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Old 12-08-2010
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k will go see be right back thanks
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Old 12-08-2010
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ok, i put a new tps on it because they brought me one they thought it was that? so i put it on and unplugged the maf sensor and it stayed running with no difference, so i plugged it back on and tried unplugging the tps, still the same ? it dont matter what i try, nothing works, i took the vacum line off teh egr valve and i have no vacuum there? this is really upsetting.help.
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Old 12-08-2010
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where is the cam sensor on this engine? and there is a sensor of some sort on the drivers side valve cover on the front end that looks like a cam sensor when i took it out? but i dont know what it is? any idea. does the book say? and i have got to get propane yet to see if injecting that helps so tommorrow ill try that and see. but if its spark would that be cam sensor?
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Old 12-08-2010
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Quote:
Originally Posted by chadd View Post
i took the vacum line off teh egr valve and i have no vacuum there? this is really upsetting.help.
The EGR has no vacuum at closed throttle but it should at part throttle.

Quote:
Originally Posted by chadd View Post
where is the cam sensor on this engine? and there is a sensor of some sort on the drivers side valve cover on the front end that looks like a cam sensor when i took it out?
99 Explorer could have a CMP on the DS valve cover depending on which engine option it has.

99 4.0 Ranger has the CMP sensor mounted on a gear drive where the distributor would have been on an older engine. It is under the rear of the upper intake manifold.
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Old 12-08-2010
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hi thanks, i dont seem to get vacuum at any time ? at the egr and mine is a 4.0 in a ranger xlt pickup with that sensor on the ds valve cover?i cant imagine what it would be? thanks again
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Old 12-08-2010
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is a 2000 different from a 99 4.0
? these guys told me it was a 99 and its actually a 9of 2000? if it makes a difference? but i usually look for myself but the door sticker has been removed sorry for this
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Old 12-09-2010
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The 2000 and earlier 4.0 Ranger is a pushrod engine with the gear driven cam sensor in the distributor position.

From 2001-on, the 4.0 Ranger engine is overhead cam with the cam position sensor on the DS cam/valve cover.
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Old 12-09-2010
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ok so there is only a cam sensor on the one side? i was wondering what that sensor was. oh and i tried spraying ether into the intake when it was acting up and it didnt make any difference it still bogged down and wanted to die? so is it a spark problem wer dealing with? it seems like it now sense the ether didnt make it speed up. any ideas ? cam sensor?
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